Covers the morphology, staining and culture features of Yersinia pestis, followed by its virulence factors shown in a table, its rodent and flea-borne epidemiology, and laboratory diagnosis. It then sets out the clinical forms of plague in a table with incubation period, the antibiotic treatment options, and prevention and control measures including chemoprophylaxis.
Topic 59 of 113 in the MU Sofia syllabus for Microbiology (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 228 words (3 min of reading), with 15 flashcards.
In this note
Yersinia pestis
General Characteristics
Virulence Factors of Y. pestis
Epidemiology
Lab Diagnosis
Clinical Forms of Plague
Treatment
Prevention and Control
General Characteristics
Family: Enterobacteriaceae
Shape: Gram-negative, small, ovoid rods
Motility: Non-motile
Capsule: Present at 37°C → protein capsule helps evade phagocytosis
Growth conditions: Facultative anaerobe
Staining: Bipolar staining seen with Giemsa or Wayson stain (safety pin appearance)
Temperature tolerance: Survives in cold, sensitive to heat
Culture: Forms rough colonies with scalloped edges and grainy appearance on nutrient agar
Biochemical:
Lactose (-)
Indole (-)
Citrate (-)
Catalase (+), Glucose (+)
Urease (-)
Epidemiology
Reservoir: Wild rodents (e.g., rats, squirrels)
Vector: Rat flea (Xenopsylla cheopis)
Transmission:
Bite of infected flea → most common route
Inhalation (droplets from infected person/animal) → pneumonic plague
Contaminated food/water (rare alimentary spread)
Geography: Still endemic in parts of Africa, Asia, South America
Lab Diagnosis
Specimens: Pus (buboes), blood, sputum (pneumonic), stool (rare)
